BUDS AND STEMS 



103 



is to compare the structures we 

 found in the bud with the markings 

 that we find on the outside of a 

 branch. Let us take for this work 

 a winter branch of the horse- 

 chestnut tree.^ Place some branches 

 in water in a warm room so that we 

 may have some opened buds to 

 look at later. 



Laboratory Suggestions. — A twig in its 

 winter condition shows the position of the 

 buds very plainly. Notice that the ter- 

 minal buds are larger than those on the 

 sides of the branch. As the twig grew 

 last year the scales covering the outside 

 of the bud dropped off and the young 

 shoot developed from the opened bud. 

 The scales which dropped off left marks 

 upon the surface of the twig, which run 

 completely around the twig at a given 

 point, forming a little ring. These rings 

 tell the age of the branch. Estimate the 

 age of the one you hold. Was the growth 

 always the same each year? How might 

 you account for the different rate of 

 growth in different years? 



Just above the lateral buds are marks, 

 known as leaf traces, that show the points 

 at which leaves were attached. A care- 

 ful inspection of the leaf traces reveals 

 certain tiny scars arranged more or less 

 in the form of a horseshoe. These scars 

 mark the former position of bundles of 

 tubes which we have already studied in 

 connection with roots. They are, in fact, 

 continuations of the same fibrovascular 

 bundles which pass from the root up 

 through the stem and out into the leaves, 

 where we see them as the veins which act 

 as the support of the soft green tissues 

 of the leaf. The most important use 

 to the plant of the fibrovascular bundles 

 is the conduction of fluids from the roots to 

 the leaves and from the leaves to the stem 

 and root. The position of the leaf traces 

 on the branch give us a clew as to the 

 appearance of the leafy tree. If we find 

 the leaf traces oppositely placed, then we 

 know that the leaves and buds, which 



Three-year-old apple branch, showing 

 terminal and lateral buds and bud 



scars. 



See Hunter and Valentine, Manual, page 25. 



